ATP-sensitive potassium (KATP) channels are a major link between cell metabolism and electrical activity, and in the heart, these channels underlie actiojn potential changes in response to ischemia. Recent evidence also supports a role in early repolarization syndrome (ERS). We have developed innovative new approaches to determine the moelcuelar details of KATP channel regulation, and to assess channel localization and function in the intact heart. During the previous period of support, we developed novel FRET approaches to assessing protein structure dynamics during gating, and to assess channel domain and subunit organization. We also developed novel transgenic animals that raise new questions regarding the role of Kir6.1 subunits in the heart. These studies now lead to three experimental series, addressing the questions regarding (1) the molecular basis of nucleotide gating in KATP, (2) the association rules between Kir6 subunits and (3) the analysis of an animal model of Kir6.1-dependent ERS. The results of proposed experiments will bring insight to the regulation and role of KATP channels in cardiac arrhythmias and will provide information that will ultimately underlie the development of rational therapies for the treatment of cardiac ischemia and arrhythmias. PUBLIC HEALTH RELEVANCE: We are studying the KATP channel which uniquely links energy levels in the heart to its excitability. Defects in this channel underlie human cardiac arrhythmias and we are attempting to understand and explain why, both by studying the innate properties of the channel itself, and by studying the consequences of defective activity in animals. The results of our studies will provide critical information for developing new therapies to treat such defects in humans.